Crucible



Feb. 5 1924. 1,482,887

c. s. cou ms CRUCIBLE Filed Aug. 30, 1920 2 Sheets-Sheet l ummmmumw WWW mum F01 flkarka' 15. Collins,

Feb. 5 1924.

C. S. COLLINS CRUCIBLE Filed Aug. 30, 1920 2 Sheets-Sheet 2 Patented Feb. 5, 1924.

UNITED STATES PATENT OFFICE.

CHARLES S. COLLINS, OF NEW YORK, N. Y., ASSIGNOR, BY MENE ASSIGNMENTS, TO THE BELLIS HEAT TREATING COMPANY, OF NEW HAVEN, CONNECTICUT, A COB/- PORATION OF CONNECTICUT.

CRUCIBLE.

Application filed August 30, 1920. Serial No. 406,870.

a crucible for containing metallic salt baths, which is of such construction that its life or period of serviceability Will be materially prolonged.

As is well known in the art, in the use of metal pots or crucibles for heating salt baths in the heat treatment of metals-a dis tress in the physical structure of the crucible is usually experienced at the higher temperatures by the oxidizing atmosphere at tackingthe pot walls. On the other hand, when the crucible is constructed of commercial graphite or other material more or less resist-ant to oxidizing atmospheres, a distress is also caused in the structure of the crucible at the higher temperatures by the action of the salts on the material, which causes it to spall, or flake off on the interior of the crucible wall.

My present invention aims to completely eliminate the above disadvantages incident to the use of crucibles constructed of metal or refractory materials, and which greatly lessens the life of the crucible. To this end, therefore, I have provided in one'embodiment of the invention a pot or crucible hav- 7 ing an external shell preferably of refractory material, and an internal shell or lining of ferrous or other base metal. This ferrous metal lining prevents the harmful action of the chemical salts above referred to, while the outer shell protects the external wall ofthe inner. liner from the effects of oxidizing atmospheres. In conjunction with the metal lining for the pot, I employ a sealing ring, which extends downwardly into the pot below the level of the salt bath, and forms an effective seal to prevent that portion of the liner wall extending above the bath, from being attacked by oxidizing atmospheres. In this manner have succeeded in materially prolonging the life or period of serviceability of the pot lining.

The present improvement. also comprehends the mounting or arrangement of the liner within the outer refractory wall of the pot in spaced relation to said wall throughout the area of its inner surface, so that there is am le freedom for expansion of the metal liner laterally, and 1n a downward direction, which will obviate the possibility of the upper flanged end of the liner being raised above the supporting plate or seat, which would admit the oxidizing atmosphere between the outer wall and the liner of the crucible.

In the production of the wellknown form of crucible consisting of a single cast steel pot, the wall of the pot is often quite porous owing to the fact that in the casting opera.- tion the metal is not poured at the correct temperature, and may also contain sand holes. Thus when subjected to high temperatures the pores in the metal open up and the bath material passing through the pores reaches the exterior surface of the pot rapid distress in the physical structure of the metal. Therefore, in another embodiment of my invention I propose to provide such a metal pot with an interior removable liner of wrought iron or pressed steel which is close grained, and non-porous, so that the salts are prevented from seeping through the wall of the liner, and entering any pores which may exist in the external cast steel protecting Wall. Thus when this external wall becomes deeply oxidized, it may be readily replaced with a new wall, while the continued serviceability of the internal metal liner for containing the bath remains unimpaired.

. Vith the above and other objects in view, the invention consists in the improved form,

construction and relative arrangement of the several parts, as will be hereinafter more fully explained, illustrated in the accompanying drawing, and subsequently in corporated in the subjoined claims.

In the drawing, wherein I have illustrated several satisfactory and practical embodi.

ments of the invention:

Figure 1 represents a vertical sectional view through a furnace having the imprgved pot or crucible arranged therein, an p Figure 2 is a similar view illustrating a slightly modified embodiment through an opening 9 in thetop wall of the supportin of the crucible.

Referring in detail to Figure 1 of the drawing, 5 designates a furnace which may be of any approved or conventional 'form, and as herein illustrated, is provided with one or more openings, such as indicated at 6, through which overflow or leakage may run 03. A supporting pedestal 7 for the pot rises centrally from the base wall of this furnace.

lln the embodiment of the invention illustrated in Figure 1 the pot or crucible includes an outer wall or shell 8,'which may be constructed or molded of graphite or other suitable materialaor alloy more or less resistant to the attacks of oxidizingv atmospheres. This'outer or body wall of the pot has a fiat base portion for engagement upon the pedestal 7, and its upper end extends furnace, and-upon the upper edge of said wall the inner edge of a flangedannulus 10 is engaged. The'outer edge of said annulus bears upon' the metal sheathing plate 11 covering the top surface of the furnace structure. i

Within the body wall 8 of the crucible an internal shell or lining 12 of metal is arranged. This lining may be of any suitable base metal alloy, such as steel, wrought iron, cast steel, etc., and preferably has a cross sectional contour conforming to the internal contour of the crucible wall 8. In the resent disclosure I have shown this liner or the body wall of the pot as provided upon its upper end with an outturned annular flange 13, seated upon the. inwardly projecting flange of the annulus 10. It will be understood, however, that in practice various other means might be adopted for the liner in position, the essential consi eration being that the wall of this metal liner throughout its area is spaced from the inner surface of the body wall 8 of the crucible, preferably, though not necessarily, in parallel relation thereto. This continuous space, indicated at 14, between the liner and the wall 8of'the crucible affords ample room for the expansion of the metal liner. both laterally and in a downward di-- rection. By spacing the bottom wall of the liner from the opposed bottom portion of the crucible wall 8, the possibilitygof the flange or other supporting means 13 on the upper end of the liner being raised, owing to longitudinal expansion, above the annulus 10, or an equivalent seating member, is entirely obviated, so that therefis no possibility of an oxidizing atmosphere entering between the metal liner and the wall 8.

Itis, of'course, understood that in practice the liner of the crucible is never com pletely with the metallic salt bath, and

i eeaee'? there would consequently remain a portion of the upper end of the metal liner which would be exposed to the oxidizing atmosphere. Owing to the fact that this metal liner becomes very highly heated, the rapid oxidization thereof would result, 50 that the liner would soon have to be removed, and a new liner substituted therefor.

In order to preclude the possibility of such oxidization of the upper end portion of the metal liner ll provide the bottomless ring or annulus 15, which is of an external diam eter less than the internal diameter of the liner, and is adapted to extend downwardly into the liner, with its lower edge below the surface of the salt bath. For the purpose of supporting this ring in position I haveillustrated the same as provided upon its upper edge with the outwardly extending annular flange 16, which rests upon the flange 13 of the liner. It is manifest, however, that various other equivalent support-' rep aced by a new one at considerably less cost than'would be involved in the re lacement of the metal liner. Moreover, I have found in practice that thesevrings 151 can still be effectively used even after they have become deeply oxidized, providing, of

course, that a suflicient body still remains to protect the upper porti'on of the pot liner, and exclude atmospheric air. Of course, the structural requirements of the ring are not comparable to those of the pot liner, which latter must always have a sufficient cross sectional areato support the weight of the bath material, in addition to its own weight.

While the ring 15 herein referred to is constructed of metal, this is not essential, as other materials might be used, and indeed future developmentsmay disclose that certain other materials or alloys are preferable. Furthermore, it is not essential that this protecting ring shall be employed in When 'the' rin 15 becomes oxidized, it may be readily onnection with a crucible of the specific construction herein disclosed. Thus it is apparent that it may also be adapted for use in connection with the ordinary pot type of furnace, without the protecting crucible, in which'provision is made for maintainin a reducing atmosphere in the combustion chamber of the furnace to prevent oxidization of the exterior of the pot wall.

In. this case the ring may be properly suspended in the up er end of the pot in a similar l erto t e cent herein disclosed when the protecting ring is used in connection with the crucible, whereby the annular dead air space will be provided above the surface of the bath material to operate as a seal, and prevent the interior of the upper end of the pot wall being attacked by oxidizing atmospheres.

In Figure 2 of the drawingsl have illustrated a crucible construction wherein an external wall8 of cast steel is provided, while the internal pot or liner 12 is formed of pressed steel, so that it is rendered nonporous, and of very close gram. Thus the bath solution contained within the pot cannot find its way through any pores which may exist in the external wall 8. There: fore, the external wall will efliciently subserve its intended purpose as a protection for the internal pressed steel liner for a relativel long period of time before renewal 0 said external wall is necessitated owing to oxidization. It will, therefore, be appreciated that such a crucible construction has a material advantage over the old construction of crucible having a single wall of cast steel of a thickness equivalent to the combined thickness of the external wall and the inner liner, as comprised in the present im rovement.

\ n connection with this form of invention the sealing ring above referred to is also preferably employed to protect the interior surface of the upper end of the liner extending above the level of the bath.

From the foregoing description it will be apparent that the bath salts do not come into contact with the external refractory wall of the crucible, while the metallic internal shell or lining does not come into contact with the products of combustion, and, owing to the provision of the protecting ring at the top of the liner, no part of the wall of this lining will be subject to the oxidizing effects of atmospheric oxygen by contact with either the internal or external surfaces of the lining wall.

It has been successfully demonstrated in practice that a pot or crucible of the construction herein described has a life or eriod of serviceability which is consideragly longer than the life of either the metallic pot or refractory crucible, as heretofore used. Accordingly, by means of the present improvement a material saving may be effected in the cost of maintenance of such ots or crucibles, since they will not require requent repair or replacement of the parts. Furthermore, by reason of this new crucible construction in practical operation, the salt bath may be permitted to freeze in the internal metallic lining without distress of its physical structure, and the necessity of laboriously bailing out the salts while in a liquid state is thus obviated with a commensurate saving of time and labor.

In the present application I have illus- I trated and described adaptations of the invention, which have been found very desir-' able and advantageous in practical use. However, the present disclosure is merely illustrative of certain practical concepts of the invention, and it is a parent that the crucible may be constructe in many different shapes and sizes, and considerably vaembodiments of the invention which are hereinafterv claimed, but it will be understood that a crucible structure having the desired characteristics might also be exemplified in other alternative forms such as would fairly come within the spirit an sco e of the invention as claimed.

claim:

1. A crucible open at its top and having an external'wall resistant to oxidizing atmospheres, and an internal wall neutral to the action of chemical salts, and means adapted to extend within the upper end of the crucible and into the salt bath to prevent atmospheric contact with the upper end of the inner wall, which extends above the level of the bath. a 2. A crucible open at its top and having an external wall resistant to oxidizin atmospheres, and an internal metalliolining for said wall, and removable means adapted to be inserted within the upper end of the lining to extend into the salt bath and exclude external air from contact with the wall projecting above the level of the at I i 3. Acrucible having an external wall resistant to oxidizing atmospheres, and an internal metallic lining for said wall, and a removable ring adapted to be inserted within the upper end of said lining, and extending below the surface level of the saltlbath to exclude external air from contact with the lining wall projecting above the bath.

4. A crucible having an external wall resistant to oxidizing atmospheres, and an internal metallic lining for said wall, and a removable ring adapted to be positioned within the upper end of said lining, and extending below the surface of the salt bath, said ring being of less diameter than the internal diameter of the lining to provide an annular dead air space between the ring and the lining wall, and thereby exclude external air from contact with the lining wall projecting above the bath.

5. A crucible having an external wall resistant to oxidizing atmospheres, and an internal metallic lining suspended within the crucible with its wall'throughout the area thereof spaced from said external wall.

. 6. A crucible having an external wall resistant to oxidizing atmospheres; and a removable internal lining having means on its open end to suspend said lining within the cruciblewith the lining wall throughput its area spaced from the external wall of the crucible.

7. A crucible having an" external wall resistant to oxidizing atmospheres, a removable internal metalliclining for said wall, having an outwardly projecting annular flange on one end, a seating member adapted to be*engaged by said flange to support the lining within the external wall ofthe crucible, and with the base portionof the linin wall spaced from the base of said externa wall, to thereby permit of longitudinal expansion of the lining wall in a downward direction and prevent lifting of the flange from'said seating member and the admission of external air between the lining andthe external wall of the crucible. v

8. For heat treating metals, a receptacle adapted to contain the treatment bath, and

means suspended within the upper open end of said receptacle and extending into the bath material to provide a seal, and thereby protect the wall of the receptacle against the attack of oxidizing atmospheres.

9; For heat treating metals, a receptacle adapted to contain a treatment bath, and a sealing ring adapted to be removably' suspended within the upper open end of said receptacle, and extendin into the bath material, to-thereby provi e an annular dead air space between said ring and the wall of the receptacle to protect the receptacle wall above the bath against the attacks of oxidiz ing atmospheres.

10. For heat treatin metals, a receptacle to contain a treatment ath, and a removablef member adapted to be arranged within the upper open end of the. receptacle, and ex- .salts, and means for protecting means?- against the influence of oxidizing atmospheres, and means extending within the upper open end of said external wall and below the surface of the bath to protect the interior surface of said internal wall above the level of the bath against the attacks of oxidizing atmospheres.

12. For heat treating metal, a crucible having an external more or less porous protecting wall, an internal non-porous metal lining to contain the bath material protected by the external wall againsttthe influence of oxidizing atmospheres, andremovablemeans ada ted to be inserted within the upper-end of t e liner to project below the level of the bath and protect the inner surface of the liner wall against the attacks of oxidizing atmospheres. l

13. A crucible open at its top and having a wall neutral to the action of chemical the inner surface of said well above the vel of the salt bath from the attacks of oxidizing atmospheres. l

14. Acrucible open at its top and having a wallneutral to the action of chemical salts, means protecting the exterior surfaces of said wall against the attacks of oxidizing atmospheres, and additional means for preventing atmospheric contact -with the inner surface of the crucible 'wall above the level of salt bath. v

In testimony that I claim the foregoing asmy invention, I have signed my name hereunder. I

up CHARLES s. coL ms 

